The present invention relates to a method for use in a telecommunication network by a data traffic policer, to a data traffic policer realizing such a method and to a telecommunication network including such a data traffic policer.
Such a method to police data traffic realized by such a data traffic policer is already known in the art e.g. from two contributions to the xe2x80x98ATM Forum Technical Committeexe2x80x99 and distributed to the xe2x80x98ATMF Traffic Management Working Groupxe2x80x99. The first one, written by O. Bonaventure, P. Frxc3xaane and E. Desmet, with the aim to stimulate the formalization of the current textual conformance definition for the Guaranteed Frame Rate service category, was made available to the public on Feb. 8-13, 1998 at Anaheim, Calif., reference 98-0059. The second one, written by O. Bonaventure and E. Desmet, with the aim to discuss the possible options for a formal Guaranteed Frame Rate GFR conformance definition and propose of choice, was made available to the public on Apr. 20-24, 1998 at Berlin, Germany, reference 98-0281. These documents will be referred to by the reference numbers 98-0059 and 98-0281, respectively, in this application.
Both documents are describing conformance definitions for the Guaranteed Frame Rate service GFR category. Data traffic policing on a data communication link is performed for data traffic including data cells being grouped into frames. Upon reception of a data cell at such a data traffic policer, the data cell is checked upon its conformance by a decision means. The decision means provides a conformance result that is either conforming or non-conforming.
According to the 98-0281 document, each arriving data cell of a frame is verified upon its conformance by a conformance test e.g. a Peak Cell Rate test PCR, or Cell Delay Variation Tolerance test CDVT according to a Guaranteed Frame Rate GFR contract of a user. In the event that the head of a frame is conforming i.e. each data cell of the head of the frame is conforming, and a non-conforming data cell arrives, the following data cells of this frame i.e. the tail of the frame, except the last cell, is also declared as non-conforming.
It has to be explained that according to the management strategy of the operator a non-conforming cell is discarded or is marked as non-conforming. Marking a non-conforming data cell is called tagging. Furthermore, the tagged data cells and tagged frames are counted by the operator.
When the non-conforming cells are e.g. discarded, the conforming cells of the same frame which are already distributed into the network, becomes part of an incomplete frame which makes these conforming data cells also non-conforming. When the non-conforming data cells are e.g. marked, according to predefined statistic rules of the operator it is decided that at a predefined amount of non-conforming traffic, a connection is interrupted which makes again that conforming frames or conforming cells which are already distributed into the network are becoming non-conforming.
In this way, the conforming head of a frame that is distributed in the network becomes an incomplete frame and this incomplete frame utilizes network resources before being discarded at its destination. This incomplete frame provides extra traffic to the network.
An object of the present invention is to provide a method for data traffic policing of the above known type but which provides an improved use of the network resources i.e. a lower percentage of non-conforming data cells being distributed in the network.
Indeed, the basic idea of the invention is based on the insight that by directly transmitting a conforming data cell, after its conformance check, into the network it is possible that it becomes later on a non-conforming data cell due to non-conformance of other cells inside the frame which cause the entire frame to be non-conforming.
However, according to the present invention the data cells are buffered into a buffer means after its conformance check while a status means keeps track of a conformance status of the frame. The conformance status of the frame is conforming as long that for each data cell of the frame that is stored in the buffer means the conformance result is conforming. A smaller risk is taken when, as long that the conformance status of the frame is conforming, only a predefined number of data cells of the frame is transmitted by a transmitting means upon reception of a predefined data cell of the frame. This will become more clear with the example of the following paragraph.
Presume a situation wherein data cells of a frame are received, checked upon its conformance and buffered by such a traffic policer. All buffered data cells have a conformance result that is conforming. This means that the frame is still treated as conforming. Upon arrival of a predefined data cell e.g. a data cell in the middle of the frame, the data traffic policer starts transmission of a predefined number of data cells e.g. a quarter of the total number of data cell of the frame, hereafter called first packet data cells. While this first packet data cells are transmitted into the network, the data traffic policer continues its work i.e. reception of the following data cells of the frame, checking its conformance and storing them into the buffer. Presume that for the nearly last data cell of the frame its conformance result is non-conforming. This means that according to the known conformance rules also the data cells received after this non-conforming data cell are declared non-conforming. As described above, all the previous data cells to this non-conforming data cell will become part of an incomplete frame and are thereby also non-conforming. However, only the first packet data cells were transmitted into the network since the other data cells are still present in the buffer. Compared to the prior art situation i.e. without a buffer, the data traffic policer of the present invention provides an improved use of the network resources i.e. a lower percentage of non-conforming data cells are distributed in the network.
An implementation of the present invention is that in the event when the frame is still treated as conforming and upon reception of the predefined data cell of the frame which is determined by the last data cell of the frame, the frame is also declared by the status means as conforming when this last data cell has also a conformance result which is conforming. The transmitting means starts transmission of a predefined number of data cells that is determined by the total number of data cells of the frame. This means that a frame is declared to be conforming when all the data cells of a frame are conforming and only when the frame is declared to be conforming all its data cells are transmitted into the network.
Another characteristic feature of the present invention is that the conformance of the data cells is checked according to cell based conformance rules or according to frame based conformance rules. Indeed, as it is described in the 98-0281 document, different options are possible for e.g. a Guaranteed Frame Rate GFR conformance definition. These options are taking into account cell related features such as the Cell Loss Priority bit, the Peak cell Rate and the Cell Delay Variation Tolerance, and also frame related features such as the Maximum Frame size. Furthermore, more than one conformance test can be executed in order to complete the conformance check according to the present invention, whereby a predefined structure is brought into the sequence of the different conformance tests.
Finally, it has to be explained that a telecommunication network that includes a data traffic policer according to the present invention can support different kinds of Quality Of Service Categories whereby the conformance is checked according to the conformance definitions of the supported service category. Such a supported service category is e.g. the unspecified Bit Rate service category or the Guaranteed Frame Rate service category.
It should be noticed that the term xe2x80x9cincludingxe2x80x9d, used in the claims, should not be interpreted as being limitative to the means listed thereafter. Thus, the scope of the expression xe2x80x9ca device including means A and Bxe2x80x9d should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
Similarly, it is to be noted that the term xe2x80x9ccoupledxe2x80x9d, also used in the claims, should not be interpreted as being limitative to direct connections only. Thus, the scope of the expression xe2x80x9ca device A coupled to a device Bxe2x80x9d should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and in input of B which may be a path including other devices or means.